CCProxy - Want to share Internet connection? Get every computer online through a single Internet connection?
Surge for Mac - Advanced Web Debugging Proxy for Mac & iOS
Apache Traffic Server - Fast, scalable and extensible HTTP/S 2 and 1.1 compliant caching proxy server.
Charles Proxy - HTTP proxy / HTTP monitor / Reverse Proxy
3proxy - 3proxy freeware proxy server for Windows and Unix. HTTP, SOCKS, FTP, POP3
HTTP Headers - HTTP Headers allows you to quickly see the HTTP header information for the current URL.